Spectroscopic study of sorption of nitrogen heterocyclic compounds on phyllosilicates

The present study focused on understanding the sorption characteristics of acridine (AcN) and acridine-9-carboxylic acid (AcNCOOH), two typical nitrog en heterocyclic compounds (NHCs), on well-characterized phyllosilicates (he ctorite, saponite, and muscovite). Results presented in this article show t hat the degree of sorption of NHCs on phyllosilicates was dependent on the nature of the participating sorbates and sorbents. Sorption of the selected NHCs was pH-dependent, with maximum sorption occurring at low pH condition s, especially at pH < pK(a) of the NHC. Though sorption of the cationic for ms of the NHCs on clays was preferred, neutral, zwitterionic, and anionic s pecies of NHCs also sorbed on the clay surfaces. Spectroscopic studies have shown that sorbed NHC molecules formed clusters on clay surfaces, which ac ted as templates for molecular aggregation. Finally, we have also found tha t the day surfaces promoted protonation of neutral AcN molecules at low sor bate concentrations.